/*
    * Copyright 2012 Daniel Kurka
    * 
    * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
    * in compliance with the License. You may obtain a copy of the License at
    * 
    * http://www.apache.org/licenses/LICENSE-2.0
    * 
    * Unless required by applicable law or agreed to in writing, software distributed under the License
   * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
   * or implied. See the License for the specific language governing permissions and limitations under
   * the License.
   */
  package com.googlecode.mgwt.dom.client.recognizer.pinch;
  
  import com.google.gwt.core.client.GWT;
  import com.google.gwt.event.shared.HasHandlers;
  import com.googlecode.mgwt.dom.client.event.touch.Touch;
  import com.googlecode.mgwt.dom.client.event.touch.TouchCancelEvent;
  import com.googlecode.mgwt.dom.client.event.touch.TouchEndEvent;
  import com.googlecode.mgwt.dom.client.event.touch.TouchHandler;
  import com.googlecode.mgwt.dom.client.event.touch.TouchMoveEvent;
  import com.googlecode.mgwt.dom.client.event.touch.TouchStartEvent;
  import com.googlecode.mgwt.dom.client.event.touch.TouchUtil;
  import com.googlecode.mgwt.dom.client.recognizer.EventPropagator;
  
  /**
   * A PinchRecognizer tracks two finger on a screen that perform a zooming / pinching action
   * 
   * @author Daniel Kurka
   * 
   */
  public class PinchRecognizer implements TouchHandler {
  
    private static EventPropagator DEFAULT_EVENT_PROPAGATOR;
  
    private final HasHandlers source;
  
    private EventPropagator eventPropagator;
  
    private enum State {
      READY, INVALID, ONE_FINGER, TWO_FINGER;
    }
  
    private State state;
  
    private Touch touchStart1;
    private Touch touchStart2;
  
    private int touchCount;
    private double distance;
  
    private final OffsetProvider offsetProvider;
  
    /**
     * Construct a {@link PinchRecognizer}
     * 
     * @param source the source to fire events on
     * @param offsetProvider the offset provider
     */
    public PinchRecognizer(HasHandlers source, OffsetProvider offsetProvider) {
  
      if (source == null) {
        throw new IllegalArgumentException("source can not be null");
      }
      if (offsetProvider == null) {
        throw new IllegalArgumentException("offsetProvider can not be null");
      }
  
      this.source = source;
      this.offsetProvider = offsetProvider;
      state = State.READY;
  
    }
  
    /*
     * (non-Javadoc)
     * 
     * @see
     * com.googlecode.mgwt.dom.client.event.touch.TouchStartHandler#onTouchStart(com.googlecode.mgwt
     * .dom.client.event.touch.TouchStartEvent)
     */
    @Override
    public void onTouchStart(TouchStartEvent event) {
      touchCount++;
      switch (state) {
        case READY:
          touchStart1 = TouchUtil.cloneTouch(event.getTouches().get(0));
          state = State.ONE_FINGER;
          break;
        case ONE_FINGER:
          touchStart2 = TouchUtil.cloneTouch(event.getTouches().get(1));
          distance = (int) Math.sqrt(Math.pow(touchStart1.getPageX() - touchStart2.getPageX(), 2) + Math.pow(touchStart1.getPageY() - touchStart1.getPageY(), 2));
          state = State.TWO_FINGER;
          break;
  
        default:
          state = State.INVALID;
          break;
     }
 
   }
 
   /*
    * (non-Javadoc)
    * 
    * @see
    * com.googlecode.mgwt.dom.client.event.touch.TouchMoveHandler#onTouchMove(com.googlecode.mgwt
    * .dom.client.event.touch.TouchMoveEvent)
    */
   @Override
   public void onTouchMove(TouchMoveEvent event) {
     switch (state) {
       case TWO_FINGER:
 
         Touch touch1 = event.getTouches().get(0);
         Touch touch2 = event.getTouches().get(1);
 
         int left = offsetProvider.getLeft();
         int top = offsetProvider.getTop();
 
         int x1 = touch1.getPageX() - left;
         int y1 = touch1.getPageY() - top;
         int x2 = touch2.getPageX() - left;
         int y2 = touch2.getPageY() - top;
 
         double newDistance = Math.sqrt(Math.pow(x1 - x2, 2) + Math.pow(y1 - y2, 2));
         int x = (x1 + x2) / 2;
         int y = (y1 + y2) / 2;
 
         getEventPropagator().fireEvent(source, new PinchEvent(x, y, distance / newDistance));
         distance = newDistance;
 
         break;
 
       default:
         state = State.INVALID;
         break;
     }
 
   }
 
   /*
    * (non-Javadoc)
    * 
    * @see
    * com.googlecode.mgwt.dom.client.event.touch.TouchEndHandler#onTouchEnd(com.googlecode.mgwt.dom
    * .client.event.touch.TouchEndEvent)
    */
   @Override
   public void onTouchEnd(TouchEndEvent event) {
     touchCount--;
     if (touchCount <= 0) {
       reset();
     } else {
       if (state == State.TWO_FINGER) {
         state = State.ONE_FINGER;
       } else {
         if (touchCount == 2) {
           state = State.TWO_FINGER;
         }
       }
     }
 
   }
 
   /*
    * (non-Javadoc)
    * 
    * @see
    * com.googlecode.mgwt.dom.client.event.touch.TouchCancelHandler#onTouchCanceled(com.googlecode
    * .mgwt.dom.client.event.touch.TouchCancelEvent)
    */
   @Override
   public void onTouchCanceled(TouchCancelEvent event) {
     touchCount--;
     if (touchCount <= 0) {
       reset();
     } else {
       if (state == State.TWO_FINGER) {
         state = State.ONE_FINGER;
       } else {
         if (touchCount == 2) {
           state = State.TWO_FINGER;
         }
       }
     }
   }
 
   protected EventPropagator getEventPropagator() {
     if (eventPropagator == null) {
       if (DEFAULT_EVENT_PROPAGATOR == null) {
         DEFAULT_EVENT_PROPAGATOR = GWT.create(EventPropagator.class);
       }
       eventPropagator = DEFAULT_EVENT_PROPAGATOR;
     }
     return eventPropagator;
   }
 
   protected void setEventPropagator(EventPropagator eventPropagator) {
     this.eventPropagator = eventPropagator;
 
   }
 
   private void reset() {
     touchCount = 0;
     state = State.READY;
 
   }
 
 }